Recently techniques have become available for the non-invasive stimulation of the human cortex and human spinal cord. A device has been manufactured which produces a high voltage, extremely brief pulse which can penetrate skull and activate central nervous system without excessive pain. Previous studies have shown it useful in some circumstances where evaluation of the speed and Integrity of motor pathways is valuable. We have succeeded in mapping the hand, arm, leg and mouth areas of the human motor cortex in normal volunteers and correlating these motor maps with the sensory maps as defined by using somatosensory evoked potentials. At this time we are studying changes in these sensorimotor maps in patients with mirror movements, stroke, and with different types of amputations. We have found that patients with congenital mirror movements have a bilateral cortical representation of each hand in the motor cortex. Also, that they have physiologically active and fast conducting connections between the motor cortex and ipsilateral muscles in the upper extremity. We have also found that EEGs do not change after a session of cortical stimulation in norma volunteers, which indicates the safety of the procedure. We have established normative data for our own laboratory for measurement of motor conduction velocities using electrical stimulation. We have stated to use magnetic stimulation and are trying to develop a technique capable of delivering focal painless transcranial stimuli.